1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing apparatus for processing a substrate.
2. Description of the Related Art
In the manufacturing process of a semiconductor device, various types of cleaning systems are employed in order to clean a semiconductor wafer (hereinafter referred to as xe2x80x9cwaferxe2x80x9d) using a cleaning liquid such as a chemical liquid and pure water, thereby removing contamination such as particles, organic contaminants, and metallic impurities, which adhere to the surface of the wafer. As one of the above cleaning systems, a wet-type cleaning system, which cleans wafers by submerging them in a cleaning liquid stored in a cleaning bath, is widespread.
Such a cleaning system performs: a cleaning process using a chemical solution mainly composed of ammonium, hydrochloric acid and fluoride acid and also using pure water; a final rinsing process using pure water; and a drying process. The cleaning system has a final rinse cleaning unit that performs the final rinsing process and a drying unit that performs the drying process.
These drying units execute, for example, an IPA vapor drying method. In the IPA vapor drying method, vapor of IPA [isopropyl alcohol: (CH3)2CHOH ], which has a high hydrophilic property, is fed onto a wafer contained in a drying chamber. Waterdrops remaining on the wafer surface are removed with volatilization of IPA, and thus the wafer is dried.
When conveying the wafer from the final rinse cleaning unit to the drying unit, the wafer surface is exposed to the air, and thus waterdrops remaining on the wafer surface are likely to be dried, producing water marks. Furthermore, the final rinse cleaning unit and the drying unit are arranged side by side, thus a large footprint is required.
With the goal of avoiding generation of water marks and reducing footprint, a rinsing/drying unit that performs both the final rinsing process and the drying process has been introduced. The rinsing/drying unit is configured so that, after completion of the final rinsing process, IPA vapor is fed when pulling up a wafer submerged in pure water stored in a cleaning bath, thereby drying the wafer by Mangorani effect stemming from the difference in surface tension between water and IPA.
However, the conventional drying device and the rinsing/drying device employ IPA, which has a property of dissolving a resist. When IPA vapor or IPA liquid is fed onto a wafer surface provided with a resist film formed according to a predetermined circuit pattern, the surface of the resist film is dissolved and the pattern might be broken. Furthermore, with the memory circuit, in the event that a dual gate for suppressing a leakage current is formed on the wafer and has a structure of locally depositing the resist film for patterning, if IPA vapor is fed to it, the dual gate is changed in thickness, and the operation of the circuit thus may be adversely affected. Furthermore, since IPA contains an alcoholic component, there is a risk of fire. As a result, sufficient safety measures and facilities are required.
Furthermore, in order to achieve the Mangorani effect sufficiently, the wafer must be raised from pure water slowly, and a considerable amount of time is thus required to move the wafer upward. In addition, a wafer guide is provided with a plurality of grooves to hold the periphery of each wafer. Water also remains in the grooves and narrow regions between the wafer periphery engaged in the grooves and on the groove surfaces. Unlike the exposed wafer surface, IPA vapor hardly reaches into these narrow regions, and thus they are hardly dried.
Therefore, an object of the present invention is to provide a substrate processing method and apparatus that can process a substrate safely, without producing water marks and without breaking a pattern of a resist film formed on the substrate.
To accomplish the above objective, the present invention provides a substrate processing method including the steps of: placing a substrate in a first processing liquid stored in a processing bath; feeding a second processing liquid different in specific gravity from the first processing liquid into the processing bath, thereby forming a first layer of the first processing liquid and a second layer of the second processing liquid with an interface being formed therebetween; and causing a relative movement of the interface and the substrate so that the substrate passes through the interface and the substrate locates on a second layer side of interface.
The relative movement of the interface and the substrate may be produced by draining the first liquid from the processing bath while feeding the second processing liquid into the processing bath.
When the specific gravity of the second processing liquid is smaller than the specific gravity of the first processing liquid, the relative movement of the interface and substrate may also be produced by moving the substrate upward.
The aforementioned method may further include a step of positioning the substrate outside the second layer and drying the substrate, after the substrate has passed through the interface by the relative movement of the interface and the substrate.
Preferably, the method according to the present invention can be used for processing a substrate having a resist film formed on the surface of the substrate. In such a case, preferably, the second processing liquid has a property of not-dissolving the resist film. The second processing liquid is preferably incombustible.
When the second processing liquid is fed, a third processing liquid may be fed, the third processing liquid being substantially insoluble in the first and the second processing liquids and having a specific gravity between those of the first and the second processing liquids is fed, thereby a third layer of the third processing liquid is formed along the interface between the first layer and the second layer, whereby the interface enters into a first layer side in the neighborhood of the point where the interface contacts the substrate.
Alternatively, the second processing liquid may be fed in a heated state into the processing bath, thereby the second layer enters into a first layer side in the neighborhood of the point where the interface contacts the substrate.
The present invention also provides a substrate processing apparatus for processing a substrate in a processing bath, which includes: a substrate holder that holds the substrate in the processing bath, a first processing liquid feed nozzle that feeds the first processing liquid into the processing bath, and a second processing liquid feed nozzle that feeds a second processing liquid different in specific gravity from the first processing liquid into the processing bath.
The substrate processing apparatus is preferably structured so that it further includes a first processing liquid draining means for draining the first processing liquid from the processing bath and a second processing liquid draining means for draining the second processing liquid from the processing bath.
The substrate holder is preferably movable up and down between inside the processing bath and above the processing bath.
Furthermore, the substrate processing apparatus is preferably structured so that it further includes a gas feeding means for feeding a gas that promotes drying the substrate.